Journal of East China Normal University(Natural Sc

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Grain size characteristics of the surface sediments from the Qian Tang River Estuary and their implication for sedimentary hydrodynamics

LIU Zhao, SHI Yu-xin, DAI Xue-rong, XI Ya-juan   

  1. School of Geographic Sciences, East China Normal University, Shanghai 200241,China
  • Received:2015-12-11 Online:2016-11-25 Published:2017-01-13


The Qiantang River estuary is a typical funnel shaped, strong tidal estuary.  It extends 274 kmlong from the tidal limit (at Luci) down to the mouth of Hangzhou Bay and possesses a complicated sedimentary hydraulic environment. This paper focuses on the grain size analysis of the surface sediments (68 samples in total)taken from the near bank underwater bottom. The grain size characteristics,types of sediments and their spatial distribution and the possible causes are discussed. Studies  have shown that the sediments are mainly composed of silt and clayey silt. According to grain size composition,the estuary can be divided into three parts: the upper, middle and the lower. The sediments from both the upper and the lower parts are finer, poorer sorted than those from the middle part.The skewness parameter (SK) is featured with sub symmetric positive bias in the upper part, while  very positively skewed positive bias in the lower part. From upstream to downstream the frequency curve shows different peak types of multipeak, high and narrow peak and low narrow peak. These differences in sediment composition and textures must have matched the different sedimentary hydrodynamic environment: the runoff in the upper part, alternative of runoff and  tide in the middle, and mainly the tidal environment in the lower. As indicated by Pejrup triangulation, the hydrodynamic environment of this estuary is relatively strong, especially in the middle part, and the grain size characteristics show close relation  to the hydrodynamic  environment.

Key words: sediments, grain size, hydrodynamic force, estuary, the Qiantang River